The brain is one example of a network (i.e., a neural network). Neural disorders are ultimately manifested as abnormal interactions in neural networks controlling specific functions. Very little is known about the workings of neural networks. Although a wealth of knowledge has been accumulated concerning the morphology, biochemistry, electrophysiology, synaptic activity and development of individual neurons, much less is known about how they work together in small or larger ensembles to accomplish their function. There are three main reasons for this lack of knowledge. First, there has been so much preoccupation with individual cells and chemicals (e.g., neurotransmitters) that neural networks as carriers of information have been overshadowed. Second, technology for studying neural networks has been largely absent. And third, the theoretical background for studying neural networks has not yielded any rigorous and robust measure of neural network function.